Just had a pro in troubleshooting my system last week and that is not the fact. 134a was designed to be compatible with R12. In fact they find that systems work better with some R12 still in the mix than with pure 134a. That's from 2 guys that do it for a living.

Hello D2TC,

Respectfully, I would defer to Mr Kollmann's advise on this. Not only did he do it for a living, he wrote the book.

This may be a case of other refer techs taking the easy way that you probably get away doing, at least for a while but could come back to bite you in the posterior down the road.

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Jeez... touchy much folks? Like I said... not my fact, it's what I got from two separate AC&R guys that don't know each other. I wasn't putting anyone down, just sharing what I've seen in the past two weeks. And I really don't know how I offended anyone by using the quote feature.
According to the guy I spoke with longest, it took 10yrs for the industry to figure out how to effectively use the 134a. The books were the books, but in practice things were different. And both guys said that old R12 systems don't need a purge. They could be both wrong... but even a journalist takes independent verification as good info.
And after the addition of 134a to my R12 system that was just a bit low, the evaporator frosted much quicker and thoroughly. So they could be wrong, my R12 mix could turn to mud tomorrow... just puttin' it out there. Don't think they'd be in business for 45 yrs if they were out trashing cooling systems, but you never know.

By all means, be safe and get a professional purge and fill.

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